The present invention relates generally to means for propelling vessels through fluid media and, more particularly, to a sail having improved aerodynamic characteristics and a method of shaping the same.
The performance of a sail boat, for instance, is determined substantially by the aerodynamic efficiency of the sail. A conventional sail comprising a single membrane of material adopts, in use, a curved shape similar to the shape of an airfoil. The efficiency of such sail, however, is limited by its thickness, i.e., the sail does not form to a full airfoil section.
Attempts have been made to provide a more efficient sail having an airfoil cross section, by constructing the sail in the form of a rigid or semi-rigid wing comprising a covering stretched over a framework. Since an airfoil cross section is asymmetric, however, such arrangements have included either an articulation allows the sail to change shape, or a pivot mechanism which allows the sail to be inverted, for the sail to be used efficiently on both tacks. The resulting mechanisms have been found structurally complex, heavy and expensive.
Other arrangements have attempted to provide a sail having an approximate airfoil cross section using a wide mast in combination with a single or double membrane sail. Although useful, such arrangements have required the expense and weight of a special mast construction and have been applicable only to sails supported up the luff by a mast.